Marie Johnson, 41, who taught math at Granada High School, entered her not guilty plea on Thursday and is scheduled to return to Alameda County Superior Court in Pleasanton on April 6 for a pretrial hearing. She remains in custody at the Alameda County Jail in lieu of $950,000 bail.

Livermore police Detective Joseph Draghi said in a probable cause arrest warrant filed in court that when police interviewed Johnson after she was arrested on Jan. 11 that she “admitted to committing the above-listed violations,” referring to the charges against her.

Johnson is charged with four counts of unlawful sexual intercourse with a minor under the age of 16 and 10 counts each of oral copulation of a person under 16 and performing lewd acts on a child.

Draghi said the alleged victim, who is now 15, told a high school coach on Jan. 10 that “he was a victim of repeated molestation” and the student “provided a detailed statement of a long term sexual relationship with Johnson.”

Livermore police spokesman Steve Goard said authorities allege that Johnson began having sex with the boy shortly after he finished taking a class from her in December 2010 and sexually assaulted the boy 24 times over a six-month period.

Police believe the alleged sexual assaults occurred in Johnson’s car and in other undisclosed locations in Livermore, according to Goard.

Investigators believe Johnson and the boy, who is now 15, formed their relationship through text messages, social networking on Facebook and instant messaging on a smartphone application called “Words with Friends,” Goard said.

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